BH92 Boom Hydraulics Weak

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
I have a L3560 HST Cab with LA805 loader and BH92 Backhoe. FEL works fine. The boom on the backhoe is very reluctant to retract when fully extended with dipperstick also at full reach, without a load in the bucket. When partially loaded, the only way the boom will lift seems to be if I curl the bucket and retract/drag the dipperstick back closer to the machine. Dipperstick and bucket seem to be working fine. Swing is also okay. Stabilizers are good although seem a little less able to lift the back of the machine than they initially could.

The backhoe was "used", sat in the dealer's lot for ??? (maybe a year or so. Original owner traded it in on a snowblower, had purchased the BH in 2015). The dealer installed a hydraulic thumb which seems to work fine, although with the weak boom it hasn't had much of a workout. When operating the bucket and dipperstick at the same time, they both move at the same time. Anytime the boom function is engaged with any other function like swing or dipperstick, the boom just stops responding. Needless to say flat, level trench bottoms are a real challenge. HST fluid is in the dipstick range and machine has just over 20 hours. All grease fittings have been greased twice. I changed the bucket from a 16" digger to a 24" ditching (no teeth) bucket and the extra weight of the bigger bucket is noticeable on the boom function. All functions seem to work at initial machine startup but as it warms up, the boom malfunctioning is more evident. The cylinders seem to get warm but not really hot.

Any suggestions and insights are greatly appreciated. Thanks.
 

edritchey

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A bunch of cute little Kubotas
Jul 19, 2014
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Sounds like it might have an internal leak probably a seal o-ring I've heard of this happen to several BH92 series backhoes when the hydraulic thumb is added. Mine had the same issue and they said it wasn't the 1st one they had have the same problem all were fine until the thumb was added. Check back with the dealer who installed the thumb I'm sure they can research the problem. My dealer is Messick's and they took care of it. ;)
 

OttoOrange

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Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
The service tech came yesterday and spent about 2 hours on the problem. Assembled a pressure fitting setup and checked operating hydraulic pressure in 3 locations ... the boom control, the dipper control and a pressure tap at the rear of the machine. All 3 read the same, about 1600 psi I think. Seems low to me, maybe? Then he replumbed the control setup to "Excavator" and discovered the boom behaved the same when controlled by a different stick. Decided the problem is in the boom cylinder, removed it to take to the shop and a teardown. Sounds good?

So now we wait some more with the tractor out of commission.
 

lugbolt

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ZG127S-54
Oct 15, 2015
4,807
1,575
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Mid, South, USA
1600 is low.

Suspect safety valve(s) debris in one or more.

'Course he could be right...if the cyl is "bad", it won't build much pressure; just leaks past internally.

But without being right there to see where he tested, it's real hard to say. He may be on the right track. That's the fun part about hydraulics; making educated guesses :)
 

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
A week after the service guy took the boom cylinder to the Shop, I finally phoned to check on its status. The Service Manager (I assume) said the following:

Apparently the cylinder is fine and really didn't have to be removed from the machine. The backhoe is supposed to operate like that. The BH77 in the Yard does the same thing ... you need to feather the controls so that one control doesn't "get" all the power. If I am around tomorrow he and the salesman will bring out the cylinder and re-install it, but will call first before they come.

That was 2 days ago. Yesterday, no phonecalls and no show. Today the same thing. I have read in other threads how much trouble some owners have had getting any satisfaction from their Kubota Dealer, and now it's happening to me. Do I really need to be the "squeaky wheel", always phoning and complaining? I guess so. It's been 21 days since I first phoned "service" and explained my problem. He was going to call me back. Never happened.

Is the BH92 backhoe really supposed to only operate one control at a time? That sure isn't what the Manual says: "With experience, the combination of both "joystick" levers will allow lift, swing, crowd out and spoil dumping, all in one smooth movement, or lowering, swing, crowd in and bucket filling with reverse movement."

I know this isn't a $300,00 HyHoe, but geez louise when the boom control by itself won't even pick up the fully extended, empty bucket and arm something must be wrong.

I guess I need a crash course in Tractor Hydraulics. I'm sure there is some good info on OTT. Any ideas or suggestions on how to proceed would certainly be appreciated.

Thanks.
 

dirtydeed

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B2650 BH77, U27-4R2, BX23TLBM, box blade, rear blade, flail mower, Stump Grinder
Dec 8, 2017
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Wind Gap, PA
Quick search says your hydraulic pressure is too low. Should be up around 2500-2600 psi. Book says 17.7 MPa. Multiply 17.7 by 145.038 to get PSI.

I'd check it at the loader valve too.
 

OttoOrange

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Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
Quick search says your hydraulic pressure is too low. Should be up around 2500-2600 psi. Book says 17.7 MPa. Multiply 17.7 by 145.038 to get PSI.

I'd check it at the loader valve too.
ok thanks ... and how do I check that? I'll need a pressure valve and a Tee connection? And just where do I connect it? Can I use the quick-connects at the FEL and / or at the rear quick-connects?

Definitely a Newbie with this stuff. Thanks.
 

dirtydeed

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B2650 BH77, U27-4R2, BX23TLBM, box blade, rear blade, flail mower, Stump Grinder
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You'll need a gauge 3000 psi min. You can build one or purchase on line or form members here (kens bolt on hooks, bxpanded etc).

You'll just need to unplug one of the loader valve couplers and plug in the gauge (should not need to TEE anything). Not sure what setup you have at the rear for hydraulic pressure testing.

Get yourself a workshop manual (WSM). Many can be had for free download.

On many series models, you can simply shim the relief valve pressure to increase it. I do not know how that's done on L series models, so be sure to get that info from someone who has knowledge on those machines.

If it has only 20 hour on it, I would assume that its still under warranty? If that's the case, don't mess with it and let the dealer fix it.
 

Dave_eng

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M7040, Nuffield 465
Oct 6, 2012
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Tractor WSM has no info on the hoe only the FEL.

There will be a separate WSM for the hoe.

Agree hydraulic pressures far too low.

Dave
 

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
You'll need a gauge 3000 psi min. You can build one or purchase on line or form members here (kens bolt on hooks, bxpanded etc).

You'll just need to unplug one of the loader valve couplers and plug in the gauge (should not need to TEE anything). Not sure what setup you have at the rear for hydraulic pressure testing.

Get yourself a workshop manual (WSM). Many can be had for free download.

On many series models, you can simply shim the relief valve pressure to increase it. I do not know how that's done on L series models, so be sure to get that info from someone who has knowledge on those machines.

If it has only 20 hour on it, I would assume that its still under warranty? If that's the case, don't mess with it and let the dealer fix it.
Thanks ... I am looking in to getting a guage rigged up. There is a Red QD male and a Blue QD female coming from separate tees on the top of the rear axle. They are plugged into the Backhoe. I assume if I remove the BH I must connect the red and blue together to get my 3 point hitch hydraulics back. Does this sound right?

There is also a 4 QD panel (all female) in red, green, yellow and blue at the back off to the side, similar to hookup at the front for the FEL. If I get a male QD hooked up to my guage can I test pressure at any of those points? What should the engine rev at?

The dealer has been rather unresponsive. But I'll keep at them.

Thanks for the info. Also trying to find a BH92 WSM ... Messicks was sold out.
 

OttoOrange

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Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
Tractor WSM has no info on the hoe only the FEL.

There will be a separate WSM for the hoe.

Agree hydraulic pressures far too low.

Dave
When the same service techie came back with the boom cylinder on Friday, I asked if he remembered what the pressure readings were ... he didn't "remember" ... it had been 10 days and I am sure he was servicing various kinds of equipment.

He may have said 2600 and not 1600 so I want to check it myself.
 

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
1600 is low.

Suspect safety valve(s) debris in one or more.

'Course he could be right...if the cyl is "bad", it won't build much pressure; just leaks past internally.

But without being right there to see where he tested, it's real hard to say. He may be on the right track. That's the fun part about hydraulics; making educated guesses :)
Are safety valves "easy to disassemble"? Still looking for a BH WSM.
 

dirtydeed

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B2650 BH77, U27-4R2, BX23TLBM, box blade, rear blade, flail mower, Stump Grinder
Dec 8, 2017
2,854
3,102
113
Wind Gap, PA
I'm not familiar with L series hydraulics, but "typically" on B and BX series units you have to connect those two power beyond hoses (that are used for the backhoe) before even starting the tractor. That will enable the three point circuit. You can check the hydraulic pressure (relief valve) pressure from any of the loader ports. just pull one of the lines off the control valve (they are color coded to let you know which circuit (loader boom or bucket). It really wont matter which as you will find out which circuit you have connected to the gauge as you move the loader joystick...one of the loader functions will not work because its deadheaded to the gauge.

Honestly, I don't know where/if the L series machines require additional shims to change relief valve pressure. I only know where to shim the relief valve on BX and B series machines. Hopefully you can find out by downloading the WSM for your tractor and/or youtube video.

I haven't refreshed my memory of your entire thread, so, I don't recall if you ever inspected the BH control linkages. If they are misaligned or have slop in them, they could also cause weak hoe symptoms as well. That should be pretty simple to check.
 

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
Thanks dirtydeed ... I wondered if the 3 point hitch might be taking hydraulic pressure (I think I read something about that in another thread) if not fully lowered, but it seems the 3 point is completely disconnected.Does that seem right?

Got to get that pressure gauge rigged up!

Thanks.
 

edritchey

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A bunch of cute little Kubotas
Jul 19, 2014
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Wellsville, PA
You probably have an internal leak in the backhoe spool valve, and yes your 3 point lever should be all the way to the lowered position.
 

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
I have finally convinced the salesman and service manger to come for a for a field test of the backhoe. Today was the day!

The weak boom lifting was observed when the dipperstick was extended and boom partially lowered. When the hydraulic thumb was jammed open, the extra oil perked the boom right up, lifting everything as it should. Conclusion, that is a very frustrating machine to try to work on all day. Overall the BH is underpowered, as it should have lifted the back of the machine or been able to rip that stump out of the ground, according to the testing personnel. Finally I am believed.

They will come tomorrow and pickup the tractor. Another month lost. We'll see what develops now, and how fast.
 

OttoOrange

New member

Equipment
L3560 with LA805 and BH92
Jun 12, 2019
13
0
1
Nova Scotia Canada
Sounds like it might have an internal leak probably a seal o-ring I've heard of this happen to several BH92 series backhoes when the hydraulic thumb is added. Mine had the same issue and they said it wasn't the 1st one they had have the same problem all were fine until the thumb was added. Check back with the dealer who installed the thumb I'm sure they can research the problem. My dealer is Messick's and they took care of it. ;)
Looks like you were right on, edritchey ... the service guys came today and discovered that jamming the hydraulic thumb "open" caused the boom to lift a whole better!

Tractor is back to the shop tomorrow, and hopefully they will get it figured out AND fixed.